The texture formation mechanism during high temperature deformation is investigated on AZ80 magnesium alloy. Three kinds of specimens with different initial textures were machined out from rolled plate having a 〈0001〉 texture. Plane strain compression tests were conducted at 723 K, 5.0×10^-2 s^-1 and strains ranging from -0.4 to -1.0. Development of (0001) 〈101‾0〉 component is confirmed regardless of the initial texture. It is concluded that the development of (0001) 〈101‾0〉 component can be attributed to the grain boundary migration during deformation. Besides (0001) 〈101‾0〉 component, several texture components appeared depending on the initial texture.

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The effect of the extrusion shape on the strength of Al–Zn–Mg–Cu alloys was investigated by measurement of the orientation distribution function (ODF) and the mechanical properties. For an extruded bar having an aspect ratio from 1 to 5, the strength in the longitudinal direction decreased with the increasing aspect ratio. For an extruded bar having an aspect ratio from 5 to 20, the strength in the longitudinal direction was nearly constant. There were no significant differences in the dispersion of fine precipitates and the electrical conductivity between the extrusion shapes. However, extrusion shapes influenced the crystallographic texture. For the extrusion shape having an aspect ratio of 1, the major orientation in the longitudinal direction was 〈111〉, for the extrusion shapes having an aspect ratio from 1 to 3, the major orientation changed from 〈111〉to 〈211〉, and for the extrusion shapes having an aspect ratio of 5 and more, the major orientation was 〈211〉. Therefore, the strength depended on Taylor's factor, or difficulty of slip toward the stress axis.

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New tentative semi-solid injection molding machine for magnesium alloy which was able to control solid fraction from 0 to 30% was developed. The solidification cracking susceptibility of the heat-resistant magnesium alloy containing 4% Al and 3% Ca fabricated by semi-solid injection molding and die-casting were investigated. The critical strain for solidification cracking of the magnesium alloy was obtained by U-type hot cracking test using in-situ observation method. High temperature ductility curve between liquidus and solidus temperatures were compared with semi-solid injection molding and die-casting. As result, solidification cracking susceptibility of semi-solid injection molding process with solid fraction of 25% was better than that of die-casting.

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The stress–strain curves in semi-solid state of Al–4.5 mass%Cu alloy, whose deformation behaviors had classified into six stages in previous study, were investigated in this study. The mechanical properties, such as elastic modulus, derived from stress–strain curves are necessary to estimate the hot tearing by CAE. Shapes of stress–strain curves in semi-solid state changed with temperature as same as deformation behaviors. Elastic modulus calculated from stress–strain curves were smaller than that calculated by general commercial software. This difference of elastic modulus was about three fingers in Pa. This difference would be caused by the melting of grain boundary and the disappearance of contact between solid phases. Elastic modulus obtained by the stress–strain curve should be more appropriate for CAE than the value calculated by commercial software.

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